Omnidirectional radio range



June 10, D, Q Q LUCK 2,422,110

O MNIDIRECTIONAL RADIO RANGE Filed Sept. 30,1942

Snventor UCK (Ittomeg Patented June 10, 1947 ZZ l@ e OMNIDIRECTIONALRADIO RANGE David G. C. Luck, Hightstown, N. J., assigner to RadioCorporation of America, a corporation of Delaware Application September30, 194,2, Serial No. 460,292

(Cl. Z50-11) 3 Claims. l

This invention relates to omnidirectional radio ranges, and particularlyto the provision of reference phase signals for such systems. One typeof omnidirectional range is described in U. S. Patent No. 2,208,376 toD. G. C. Luck. A. continuous wave carrier is radiated with a limacoiddirective pattern. The directive pattern is continuously rotated, sothat the signal picked up by a receiver is sinusoidally modulated at thepattern rotation frequency. The modulation phase depends on thedirection of the receiver from the transmitter. It is necessary toprovide a constant phase reference for comparison with the patternrotation 'modulation at the receiver in order to provide azimuthindication. 'Ihis has been done by impressing the reference signal on asubcarrier, or by distorting the reference signal to an impulsive shape,so that as the modulation peak occurs due north of the transmitter, foreX- ample, a brief impulse is radiated.

The principal object of the present invention is to provide an improvedomnidirectional radio range with an improved reference phasetransmission, in which the use' of a subcarrier or of impulsive keyingis avoided.

Another object is to provide an improved omnidirectional radio rangesystem affording coarsel and ne azimuth indications.

In accordance with this invention, the directive transmission is made bycausing a eld pattern to rotate at a uniform speed, while the referencetransmission is made by modulating a non-directionally transmittedcarrier at a frequency subharmonically related to the pattern rotationfrequency. The non-directional carrier is of the same frequency as thatused for the directional transmission. A fixed phasal relation ismaintained at the transmitter between the pattern rotation and thenon-directional modulation.

At the receiver the pattern rotation and reference modulations areseparated by lilters. The frequency of the reference modulation ismultiplied to equal that of the directional modulation, and the relativephase of the two voltages indicated by a synchroscope, or the like.

Referring to the drawing, Fig. l is a schematic block diagram of a rangetransmitter according to the invention, and Fig. 2 is a similar diagramof a range receiver.

At the range transmitter, orthogonally related pairs of opposed antennasN S and E, W are connected to the outputs of a pair of balancedmodulators I and 3, respectively. A radio frequency oscillator 5 isconnected through an amplifier l a. to the modulators I and 3 and to apower amplier 9. The amplifier 9 is connected to a nondirective antennaI I.

An oscillator I3 is connected through a frequency divider I5 to thebalanced modulator I. The output of the frequencydivider I5 is alsoconnected through a 90 phase shifter I'I to the balanced modulator 3. Asecond frequency divider I9 is connected between the output of thefrequency divider I5 and a combining circuit 2I. A modulator 23 isarranged to modulate the power amplifier 9 under the control of theoutput of the combining circuit 2|.

Fig. 2 is a schematic block diagram of a range receiver system accordingto the invention. A radio receiver 25 is connected to an antenna 2l. Theoutput of the receiver 25 is connected to lters 29, 3l and 33. Theoutput of the lter 29 is connected directly to one of the usualorthogonally related deflection circuits of a cathode ray tube 35 andthrough a'90 phase shifter 3l to the other deflection circuit of thetube 35.

The output of the iilter 33 is applied to a frequency multiplier 34,which is similarly connected to the orthogonal deflection circuits of asecond cathode ray tube 39. A second 90 phase shifter lll is providedfor the tube 39. The cathode ray tubes 35 and 39 are provided withradial deflection electrodes. The radial deflection electrodes of thetwo tubes are connected together through an impulse Shaper circuit 43 tothe output of the lter 3|.

The operation of the system is as follows: The oscillator 5 provides acarrier voltage which is amplied by the amplier 'I and applied to thebalanced modulators I and 3 and the power amplier 9. The oscillator I3provides a frequency of, for example, 720 cycles per second. Thefrequency divider I5 is adjusted for l2 to 1 frequency division,providing an output of cycles per second. This voltage controls thebalanced modulators I and 3, providing a rotating eld of radiation fromthe antennas N, S, E and W, as described more fully in theaforementioned patent. The output of the ampliiier 3 is radiatednon-directionally by the antenna I I, modifying the iigure-of-eightlpattern of the antennas N, S, E and W to provide the limacoid pattern.

Reference phase modulation is impressed on the non-directional carrierby modulation of the power amplifier 9. The frequency divider I0 isarranged for 3 to 1 division, providing an output of 20 cycles persecond for controlling the modulator 23. To provide iine indications ofazimuth,

as will appear more fully hereinafter, the output cathode ray beam ofthe tube 35Y to trace a circular path at the rate of '720 times persecond. The 20 cycle component is converted to 60 cycles by themultiplier 3G, causing the beam of the tube 39 to trace a circular path60 times per second. YThe 60 cycle variable phase modulation componentis vconverted by the impulse Shaper 43 to a sharp pulse repeating atintervals of onesixtieth second, coinciding with the peaks of themodulation from which it is derived. This pulse is applied to the radialdeflection circuits of both cathode ray tubes 35 and 39, providingdeflections 45 and lll of the traces i9 and 5l.

The coarse indicator tube 39 traces one circle for each pulse, while thefine indicator 35 traces l2 circles during the same period. The face ofthe tube 39 may be calibrated to indicate angles up to one-twelfth of acircle, or 30 degrees. Thus the tube 39 indicates the approximatebearing of the range transmitter as over 30 and less than 60, and thetube 35 shows that the exact bearing is eleven and one-half degrees eastof the rst full thirty degrees. The exact bearing is th-us 30` plus 11%,or 4119 Thus the invention has been described as an improved method ofand means for providing reierence phase transmission for omnidirectionalradio ranges. A constant phase modulation at a subharmonic of thepattern rotation frequency is impressed on the non-directional carrierradiated by the sense antenna of the range transmitter array. The rangereceiver is provided with filters for separating the referencemodulation from the pattern rotation modulation. The referencemodulation is multiplied in frequency to provide a constant phaseVoltage equal in frequency to the variable phase directional modulationvoltages. The two voltages are applied to a phase indicator calibratedto read azimuth.

I claim as my invention:

1. An omnidirectional radio range system including means for radiating aradio frequency carrier in a rotating directive eld pattern and meansfor changing the shape of said pattern cyclically at frequenciesharmonically related to the frequency of said pattern rotation wherebysaid carrier is modulated at one frequency with a phase depending uponazimuth and at other frequencies independent of azimuth, means forreceiving and demodulating said carrier to produce a signalcorresponding to the composite modulation thereof, lter means arrangedto separate the components of said signal, means arranged to change thefrequency of one of said components to a frequency equal to that of saidpattern rotation, a phase responsive indicator device arranged tocompare said latter component with the modulation derived from saidpattern rotation to provide a coarse unique indication, and a secondphase responsive indicator device arranged to compare said patternrotation modulation component with a higher :frequency component toprovide a ne indication.

2. An omnidirectional radio range system, including means for radiatinga carrier wave including two modulation components of constant azimuthalphase and means for radiating a suppressed carrier wave including amodulation component of phase depending upon azimuth, said threemodulation components being of different and harmonically relatedfrequencies; a receiver including means for demodulating said carrierWave and means for separating said modulation components of differentfrequencies, means for changing the frequency of one of said constantphase components to a frequency equal to that of said component ofvariable azimuthal phase, means for comparing said frequency changedcomponent with said variable phase component to provide a unique coarseindication of azimuth, and means for comparing the other of saidconstant phase components with said variable phase component to providea ne indication of azimuth.

3. In an omnidirectional radio range, the method of providing azimuthinformation including the steps of radiating a suppressed carrier wavewith a modulation component of phase depending upon azimuth radiating acarrier wave with two modulation components of constant phases, saidthree modulation components being of different and harmonically relatedfrequencies, receiving and demodulating said waves, separating saidmodulation components of different frequencies, changing the frequencyof one of said constant phase components to a frequency equal to that ofsaid component of azimuthally dependent phase, comparing said frequencychanged component with said constant phase component to provide a uniquecoarse indication of azimuth, and comparing the other of said constantphase components with said component of azimuthally dependent phase toprovide a iine indication of azimuth.

DAVID G. C. LUCK.

REFERENCES CETED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,129,004 Greig Sept. 6, 19382,252,699 Byrne Aug. 19, 1941

